Partially lined disk brake with electromechanical actuator unit

ABSTRACT

The present invention relates to an electromechanically actuated partially lined disk brake suitable both for realizing driving and parking brake functions. For this purpose, the partially lined disk brake comprises a brake caliper with an electromechanical actuating unit, by means of which the partially lined disk brake can be clamped by way of at least one interposed actuating element. The object of the invention is to achieve a compact design and a parking brake that can be actuated electrically. The brake caliper includes a multi-step reduction gear arranged between the integrated actuating unit and an actuating element. The actuating unit, reduction gear and actuating element are arranged in a recess of the brake caliper that is configured as a housing. According to the invention, the multi-step reduction gear is configured as a non-self-locking device, i.e. exhibits an overall efficiency of η&gt;50%, and also is provided with an engageable freewheel, by means of which both driving and parking brake functions can be realized.

TECHNICAL FIELD

The present invention generally relates to vehicle brakes and moreparticularly relates to an electromechanically actuated partially lineddisk brake that can be used both for regular braking functions andparking brake functions.

BACKGROUND OF THE INVENTION

This kind of electromechanically actuated disk brake is known from EP 0728 089 B1. The disk brake described therein has a floating brakecaliper as well as an actuating unit arranged on the brake caliper. Theactuating unit exhibits an electric motor which sets an actuatingelement by means of an interposed reduction gear. The actuating elementcauses one of two brake linings displaceably arranged in the brakecaliper to come into contact with a brake disk. The second brake liningalso is pressed onto the brake disk by a reaction force acting on thebrake caliper. Despite its compact structural design, this disk brakehas a drawback in that it can only develop a limited braking force inboth driving and parking brake functions.

DE 197 32 168 C1 describes a hydraulic vehicle brake with parking brakedevice, where a brake piston is arranged displaceably within a hydraulicchamber of the vehicle brake. The brake piston can be shifted into anactuating position within the brake caliper by means of hydraulicpressure: it acts together with a brake lining in such a way that thebrake piston presses the brake lining against a brake disk. In order toensure that, in addition to its function as a hydraulic driving brake,the vehicle brake also can be used as a parking brake, a spindle-and-nutconfiguration, which is driven by an electric motor, is arrangedco-axially to the axis of the brake piston. Furthermore, a complexreduction gear is required in addition to an electric motor to generatethe necessary clamping forces for a parking brake function. Thus, theabove-mentioned vehicle brake needs two independent actuating paths,namely an hydraulic and an electromechanical one. This in turn requiresa complex overall design of the vehicle brake and a complicated processfor operating or controlling the vehicle brake.

The object of the present invention is to provide an electromechanicallyactuated partially lined disk brake that has a simple design and can beused both as a driving and parking brake and can be operated witheconomic efficiency and comfortably.

This object is solved by means of an electromechanically actuatedpartially lined disk brake of the present invention. Accordingly, thepartially lined disk brake of the present invention comprises a brakecaliper with an electromechanical actuating unit having at least twobrake linings displaceably arranged in the brake caliper, each of whichacts on a friction surface of a brake disk and one of which is broughtinto contact with the brake disk by means of at least one actuatingelement. In terms of effect a multi-step reduction gear is arrangedbetween the actuating unit and actuating element, with the actuatingunit, reduction gear and actuating element being located in a recess ofthe brake caliper that is configured as a housing. This allows aparticularly compact design of the brake caliper, with the brake caliperbeing able to realize both the driving and parking brake functions. Allin all, the multi-step reduction gear is configured as anon-self-locking device, i.e. it exhibits an overall efficiency ofη>50%. Thus, the clamping force from the electromechanical actuatingunit to the brake linings is transmitted with as little loss as possibleand, consequently, very efficiently. In addition, an engageablefreewheel acting together with the reduction gear is included. By meansof this engageable freewheel it is possible, in the event of activation,to lock the clamped brake caliper like a return stop in order to realizethe parking brake function. In the direction of rotation of clamping ofthe actuating unit or non-self-locking reduction gear, the transmissionof the brake clamping force from the actuating unit to the brake liningsis not affected.

A particularly advantageous embodiment of the partially lined disk brakeis achieved by having the reduction gear comprise a rolling-elementramp-type gear. This type of gear allows a rotary input variable to beconverted into a translational output variable while ensuring a highreduction ratio. For this purpose, the rolling-element ramp-type gearpreferably exhibits several ramps concentrically residing one insideothers, allowing a large usable angle of torsion. The translationalstroke of this type of gear is coordinated with the respective actuatingstroke of the brake piston, in particular the translational strokecorresponds to this actuating stroke. For this purpose, therolling-element ramp-type gear preferably comprises two ramp halves thatcan be twisted relative to one another; of these, the first ramp half isconnected to the electromechanical actuating unit at the output end anda second ramp half is operatively connected to the actuating element.When the partially lined disk brake is operated, the two ramp halves canbe twisted against one another to generate the actuating stroke and totransmit this to at least one of the brake linings via the actuatingelement. Preferably, the second ramp half, i.e. the one that isoperatively connected to the actuating element, is secured againsttwisting; however, it must be possible to shift it in the housing of thebrake caliper by the size of the actuating stroke of the brake lining.

According to a preferred embodiment of the invention, the engageablefreewheel is designed as a return lock that is effective in thedirection opposite to the direction of rotation of clamping of thereduction gear. When the brake is clamped, this return lock does notaffect the function of the reduction gear. The non-self-lockingreduction gear is prevented from reversing only in a clamped state andwhen the freewheel is blocked. Hence, the brake can be locked in aclamped state and, thus, secured against release of the brake due todecreasing clamping force of the brake. In order to release the brake,the lock function of the freewheel can be deactivated by means of aswitching function when the reduction gear is rotated in the directionof release.

According to an advantageous embodiment of the invention, the multi-stepreduction gear comprises a planetary gear step connected to theelectromechanical actuating unit at the driving end as well as a spurgear step connected thereto, which acts together with therolling-element ramp-type gear at the output end. By means of theplanetary gear step in connection with the spur gear step, aparticularly high step-down ratio is achieved for the entire reductiongear despite very low space requirements.

A particularly effective and easy-to-realize embodiment of the partiallylined disk brake according to the present invention is achieved byproviding the actuating element with a brake piston that is displaceablyarranged in the brake caliper as well as at least one brake pistonoperatively connected to a brake lining, which is connected to therolling-element ramp-type gear at the output end. As regards the overalldesign of the brake caliper in this connection, well-known designfeatures of a brake caliper with a hydraulic actuating unit may beapplied.

In order to maintain constant the translational stroke of the reductiongear when operating the partially lined disk brake, the actuatingelement preferably comprises also an adjusting device that isdisplaceably arranged in the brake caliper and can be extended in theclamping direction of the partially lined disk brake, wherein suchadjusting device is operatively connected to at least one brake liningon the one hand and to the rolling-element ramp-type gear at the outputend on the other hand. The extendable adjusting device takes intoaccount the wear of the brake linings and is extended in proportion tothe wear of the brake linings. Each actuating stroke of the brake pistonor the stroke of the ramp half of the rolling-element ramp-type geararranged displaceably in the direction of clamping in the brake caliperhousing is maintained over the entire service life of the brake. In anadvantageous design, the adjusting device includes a nut-and-spindleconfiguration which acts together on the one hand with the brake pistonand on the other hand with the rolling-element ramp-type gear. Nut andspindle are connected by a thread in such a way that they can be twistedin relation to one another, with the spindle being connected in atwist-proof manner to the second ramp half arranged displaceably in thebrake caliper housing.

According to another advantageous embodiment of the invention, thepartially lined disk brake exhibits a hydraulic actuating device that isindependent of the electromechanical actuating unit. In particular, thishydraulic actuating device is formed by a cylinder bore in the brakecaliper in connection with the brake piston. Within such a configurationthe hydraulic actuating device can be used for driving brake operationsand the electromechanical actuating unit for parking brake operations.Thus, the two different modes of actuation can be designed andconfigured specifically for their respective function.

A particularly low-cost partially lined disk brake according to thepresent invention is achieved when the electromechanical actuating unitis formed by a direct current (DC) electric motor. Such electric motorsare known in many different designs and can be used within the brake asa standardized component.

In a preferred embodiment of the partially lined disk brake, theelectric motor has an angular-position sensor that is connected to therotary movement of the electric motor, in particular can be integratedin the reduction gear or electric motor. Thus the current motor positionand motor movement with direction of rotation and speed can be detectedat any time and, consequently, provides information on the correspondingactuating state of the partially lined disk brake.

According to a further embodiment of the invention, the reduction gearis provided with a tool holding fixture to attach an emergency actuatingelement. In this way, an emergency actuation of the brake, i.e.releasing or clamping, is possible in the event of a malfunction, e.g.when there is no sufficient electric power supply.

An advantageous embodiment of the invention is achieved when at leastthe electromechanical actuating unit, planetary gear as well as adriving wheel of the spur gear form a first independent subassembly,which is arranged and fixed in the recess of the brake caliper that isconfigured as a housing. Furthermore, this first subassembly can besupplemented by additional meaningful single parts. Hence, this modulecan be preassembled simply outside the brake caliper and, after beinginserted in the recess of the brake caliper, it can, for example, befastened with screws. In the same way, it would be meaningful for atleast the rolling-element ramp-type gear, engageable freewheel as wellas an output wheel of the spur gear to form another independentsubassembly. This second subassembly also can be preassembled and,finally, fastened in the recess of the brake caliper that is configuredas a housing. These subassemblies give rise to a particularlyeasy-to-assemble modular design of the partially lined disk brake.

According to a preferable embodiment of the invention, theelectromechanical actuating unit, actuating element as well asmulti-step reduction gear are arranged and fastened within the brakecaliper and sealed off against their surroundings by means of a housingcover. Thus, a particularly compact design is achieved for the brakecaliper and, also, the individual assemblies of the partially lined diskbrake can be accessed quickly and in an easy-to-assemble manner simplyby removing the housing cover. The housing cover prevents contaminationof the individual subassemblies and, hence, ensures safe operation ofthe brake.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectioned view of an embodiment according to theinvention, showing a combined brake caliper of a partially lined diskbrake for driving brake and parking brake functions.

FIG. 2 is a view of the brake caliper taken substantially along the line2—2 shown in FIG. 1.

FIG. 3 is a view of the brake caliper along the line 3—3 in FIG. 2.

FIG. 4 is a view of the brake caliper along the line 4—4 in FIG. 2.

FIGS. 5A-5C provides several cross-sectional views of an embodiment ofthe rolling-element ramp-type gear with a freewheel.

FIGS. 6A-6D provides several cut views of an embodiment of a ramp halfof the rolling-element ramp-type gear.

DETAILED DESCRIPTION ON THE PREFERRED EMBODIMENTS

The combined brake caliper 1 of a partially lined disk brake shown inFIGS. 1-4 is suitable for realizing both driving brake and parking brakefunctions. It is designed as a floating caliper, i.e. it is mounteddisplaceably in relation to the clamping direction of the partiallylined disk brake by means of guide bush 2 of a pin guide (not shown) ona brake holder attached to the vehicle. Brake caliper 1 overlaps withone bridge section 3 a brake disk that is not shown as well as brakelinings arranged on both sides of the brake disk, which tribologicallyact on the brake disk in a known manner. In this respect, one of thebrake linings is connected to brake piston 5 mounted displaceably incylinder bore 4. The other brake lining is connected to a brake caliperside 6 lying axially outside the vehicle axis. The actual clamping forceof the floating caliper-partially lined disk brake is transmitted in theknown manner to the inner brake lining by means of brake piston 5 actingas actuating element. Due to the reaction force and the ensuingdisplacement of the brake caliper, the outer brake lining is alsopressed against the brake disk.

In order to generate the required clamping force, a hydraulic actuatingdevice 7 on the one hand and an electromechanical actuating unit 8 onthe other hand are provided in brake caliper 1. The hydraulic actuatingdevice 7 essentially comprises the cylinder bore 4 as well as the brakepiston 5 and usually is provided for the driving brake function. Forthis purpose, the hydraulic pressure chamber formed by cylinder bore 4and the inside of brake piston 5 is sealed off against the surroundingsby means of sealing elements 9.

The electromechanical actuating unit 8 essentially is responsible forrealizing the parking brake function and acts on the inner brake liningvia an interposed multi-step reduction gear 10 as well as actuatingelement 11. For this purpose, the electromechanical actuating unit 8 isintegrated in brake caliper 1 together with reduction gear 10 andactuating element 11 and located in recess 12, 12′ of the brake caliperthat is configured as a housing. The electromechanical actuating unit 8preferably is designed as an electric motor. In this case, it shouldparticularly be a DC motor and, hence, a standardized motor design canbe used. Within brake caliper 1 the electric motor 8 is held on bothsides via bearing bush 13 as well as bearing plate 14.

Actuating shaft 15 with sun wheel 16 attached to it is configured at theoutput end of electric motor 8. Sun wheel 16 is part of planetary gear17 connected to actuating unit 8, which provides a high reduction of themotor speed while simultaneously increasing the torque.

Planetary gear 17 comprises planet carrier 18 with planet wheels 19,which become engaged in ring gear 20, wherein ring gear 20 is eitherformed firmly onto the brake caliper or, as shown in FIGS. 1-4,integrated in bearing plate 14, which is screwed together with brakecaliper 1. At the output end planetary gear 17 is connected to spur gear21, which comprises a driving wheel 22 and output wheel 23. At the sametime, the speed at the output end of planetary gear 17 is transmitted toangular position sensor 26 via sensor shaft 24 with gearwheel 25. Thus,angular position sensor 26 is connected to electric motor 8 and, hence,allows the current determination of the angular position or rotarymotion of electric motor 8 in relation to the direction of rotation andspeed of rotation. Finally, this provides information on the currentactuating state of the brake. Angular position sensor 26 can be realizedin a particularly simple manner by means of a Hall sensor. For thispurpose, it generally is necessary to have a connection to the rotarymotion of electric motor 8, so that angular position sensor 26 can belocated directly on electric motor 8 or a suitable position of reductiongear 10. In this connection, it is recommended that angular positionsensor 26 be arranged as closely as possible to electric motor 8 due tothe high speeds and, consequently, high resolution.

The spur gear step 21 following at the output end of planetary ear 17causes another reduction in speed as well as increase in torque andserves to drive a rolling-element ramp-type gear 27 that is arrangedcoaxially to brake piston 5. Rolling-element ramp-type gear 27 inparticular comprises several highly reducing ramp configurations whichare formed onto two ramp halves 28, 29 in the shape of ramp guideways30, wherein the two ramp halves 28, 29 can be twisted in relation to oneanother. Ramp guideways 30 are described in more detail in FIG. 6, usingthe second ramp half 29 as an example. Preferably they are two rampguideways 30 that are concentrically arranged one inside another andadditionally shifted by 180° in their angular position. Both rampguideways have the same slope. Rolling-type bearing elements 36, inparticular balls or rolls, which can roll in the ramp guideways 30 arearranged in ramp guideways 30. In order to increase the gear stroke atthe output end, it is advantageous to provide ramp guideways 30 in sucha way that they correspond to one another on both ramp halves 28, 29.The arrangement of ramp guideways 30 residing one inside anothertogether with the angular displacement of ramp guideways 30 as comparedto known ramp configurations allows an additional increase in thestep-down ratio of rolling-element ramp-type gear 27. This also isachieved through the substantially increased twisting angle of the tworamp halves 28, 29 as compared to known ramp configurations, which ispossible through the arrangement of ramp guideways 30. Hence, useabletwisting angles up to about 270° can be realized.

The first ramp half 28 is connected in a twist-proof manner to outputwheel 23 of spur gear 21 and arranged on bearing 38 in brake caliper 1via a hollow shaft 37. For this purpose, hollow shaft 37 with bearingbush 39 is held rotatably in a traverse 40. Traverse 40 exhibits veryhigh strength, i.e. it is preferably made of steel, and is firmlyscrewed to brake caliper 1. In contrast, the second ramp half 29 isresistant to twist; however, it can be displaced in recess 12′ of brakecaliper 1 in the direction of the brake piston axis 31. For thispurpose, a bush 41 is fastened in a twist-proof manner in brake caliper1, preferably by being pressed in firmly, and the second ramp half 29 inturn is arranged in a twist-proof manner on bush 41. For this purpose,the second ramp half 29 preferably has recesses 42 on its surface areawhich act together with appropriate beads of bush 41. A correspondingway of ensuring protection against torsion by means of recesses andappropriate beads also can be used between bush 41 and brake caliper 1.Preferably bush 41 has an outer knurling 48 at one end and is firmlypressed into brake caliper 1 with this end. However, the exact design ofthis protection against torsion is not decisive for the presentinvention. Configurations ensuring protection against torsion that workanalogously, which fix the second ramp half 29 in a twist-proof mannerin brake caliper 1 also are possible. The two ramp halves 28, 29 arepressed together by spring 43, and the rolling-type bearing elements 36are always held in their correct position within the ramp guideways.

In detail, rolling-element ramp-type gear 27, by twisting the two ramphalves 28, 29 against one another, causes rolling-type bearing elements36 to roll in ramp guideways 30. On the one hand this gives rise to avery high step-down in speed and on the other hand causes the rotaryinput variable (speed of the spur gear 21 at the output end) to beconverted into a translational output variable (gear stroke) in the formof a “rotational-translational-gear”. A gear stroke in the direction ofthe brake piston axis 31 is generated as the translational outputvariable. When brake caliper 1 is clamped electromechanically by meansof actuating unit 8, this gear stroke is transmitted to brake piston 5by way of a mechanical adjusting device 32, which acts as an actuatingelement. In this connection the gear stroke essentially corresponds tothe clamping stroke of the brake piston.

Adjusting device 32 takes into account the wear of the brake linings andcompensates for this by extending in the direction of the brake pistonaxis 5. Thus, the required clamping stroke of brake piston 5 and,consequently, the gear stroke of rolling-element ramp-type gear 27 canbe held constant. Adjusting device 32 is connected in a twist-proofmanner to rolling-element ramp-type gear 27 on the one hand and to brakepiston 5 on the other hand. It can be extended in the direction of thebrake piston axis 5 and essentially comprises a nut-and-spindleconfiguration with a spindle 33 attached in a twist-proof manner to thesecond ramp half 29 and a nut 34 arranged rotatably on spindle 33, whichis supported on brake piston 5. Nut 34 and spindle 33 are tensionedagainst one another by means of several springs 35, so that theadjusting device 32 is extended in the direction of brake piston axis 31when the brake linings show signs of wear. The basic design of such anadjusting device 32 as well as its function are known and shall not beexplained in more detail here. With respect to further details of theadjusting device 32 as regards design and function, please refer to DE195 21 634 A1. The characteristics of the adjusting device mentionedthere can be used for the present invention.

Basically the entire, multi-step reduction gear 10 with planetary gear17, spur gear 21 and rolling-element ramp-type gear 27 is designed toachieve high overall efficiency. Hence, reduction gear 10 exhibits anoverall efficiency of η>50%, i.e. reduction gear 10 is anon-self-locking device.

In order to implement a parking brake function when the brake is clampedelectromotively by means of actuating unit 8, it is therefore necessaryto lock brake caliper 1 in the clamped state. This is realized by anengageable freewheel 44 that acts together with rolling-elementramp-type gear 27. The engageable freewheel 44 is arranged betweenoutput wheel 23 of spur gear 21 and the first ramp half 28. It workslike a return lock. In the rotary clamping direction of actuating unit 8as well as the reduction gear 17 or in the rotary clamping direction 50of the first ramp half 28 the freewheel 44 always travels freely anddoes not obstruct transmission of the clamping forces to the two brakelinings that are not shown. If, however, brake caliper 1 is in a clampedstate, the reaction force resulting from the clamping force is taken upby rolling-element ramp-type gear 27 via brake piston 5 and adjustingdevice 32. Due to the high degree of efficiency, the first ramp half 28tends to turn in the direction of the “release brake”. However, this isprevented by the freewheel 44. For this purpose, clamping elements 46,preferably clamping rolls, to each of which the spring force of apressure spring 45 is applied, roll along a sloped guide surface 47 andjam the first ramp half 28 with respect to brake caliper 1 or interposedbush 41. Thus, rolling-element ramp-type gear 27 is fixed in place andundesired unclamping of brake caliper 1 is prevented. For this purpose,output wheel 23 and the first ramp half 28 are connected to one anothervia pins 51 as regards their rotational movement, with there beingclearance between output wheel 23 and first ramp half 28. Pins 51 areattached to the first ramp half 28 and protrude in the direction ofoutput wheel 23, extending into associated recesses 52 of output wheel23 by forming the above-mentioned clearance. Through this clearancefreewheel 44 is locked by the reaction force of the brake clampingforce, and the brake clamping force is maintained. This also applieswhen the electric motor 8 is switched off. Hence, the parking brakefunction can be realized.

To loosen brake caliper 1 after electromotive actuation, the actuatingunit 8 is operated in the direction of rotation of release. Thus,reduction gear 10 also causes the first ramp half 28 to turn in thedirection of rotation of release. Output wheel 23 and the actuating pins53 connected in a twist-proof manner thereon rotate slightly withrespect to the first ramp half 28 jammed with brake caliper 1, withouttransmitting any torque at first due to the clearance. This relativetwist of output wheel 23 and ramp half 28 causes the clamping elementsto be loosened because actuating pins 53 extending into the first ramphalf 28 push clamping elements 46 from their lock position and releasethe freewheel 44. The position of actuating pins 53, pins 51, recesses52 as well as clamping elements 46 in their lock position is coordinatedin such a way that—in order to release the locked freewheel 44—actuatingpins 53 come into contact with clamping elements 46 first and releasethe lock function before pins 51 become engaged with the associatedrecesses 52 in order to transmit torque. Thus, the switching function offreewheel 44 allows the rolling-element ramp-type gear 27 to be unlockedby operating the actuating unit 8 in the release direction of rotationand, hence, release of the brake. As shown in FIGS. 4 and 5, the numberof actuating pins 53, pins 51, clamping elements 46 as well as pressuresprings 45 is not limited to a certain number according to theinvention. The figures merely show advantageous embodiments.

Arranging the electromechanical actuating unit 8 parallel to the brakepiston axis 31 allows a particularly compact design for brake caliper 1on the one hand and the possibility of a modular design on the otherhand. Such a first subassembly essentially comprises actuating unit 8,planetary gear 17, bearing plate 14 with hollow wheel 20, angularposition sensor 26, drive wheel 22 as well as a ear cover 54. Due to thegear cover 54 this first subassembly can be preassembled outside brakecaliper 1 and finally mounted in brake caliper 1 with fastening screws55. Gear cover 54 also serves for holding sensor shaft 24 and drivewheel 22 of spur gear 21. In addition, the electric lines 56 foractuating unit 8 and angular position sensor 26, as shown in FIG. 3, runthrough gear cover 54 or are guided through it.

Furthermore, a second subassembly comprising rolling-element ramp-typegear 27, engageable freewheel 44, output wheel 23, hollow shaft 37 withbearing bush 39 as well as bearing 38 and traverse 40 can be formed. Forthis purpose, hollow shaft 37 is connected by bearings to traverse 40via bearing bush 39 and bearing 38. Bearing 38 can be designed as athrust bearing or angular ball bearing or shoulder bearing in order toimprove the radially effective bearing properties. This secondsubassembly also can be preassembled as an independent module outsidebrake caliper 1. After the second subassembly is mounted in recess 12′of the brake caliper, screws are used to attach the subassembly to brakecaliper 1 via traverse 40. For this purpose, traverse 40 and screws 57have to be stable, since they are used for taking up the reaction forceof the brake clamping force.

Finally, brake caliper 1 is closed by means of a housing cover 58, whichseals off brake caliper 1 against its surroundings. For this purpose,housing cover 58 exhibits several bent straps 59 distributed along itscircumference, and these are used for fastening it to an associatedcollar 60 on brake caliper 1. To improve the tightness of the seals, anadditional seal 61 can be provided between housing cover 58 and brakecaliper 1. The electric supply line 62 for actuating unit 8 and angularposition sensor 26 also is led through housing cover 58.

In order to implement a mechanical emergency actuation of the brake,e.g. when there is a power failure, a hole locked with a removable stop63 is provided in housing cover 58. This hole provides access to a toolholding fixture 64 at the drive wheel 22 of spur gear 21. When asuitable tool is inserted in the tool holding fixture 64, the reductiongear 10 can be rotated to loosen or clamp the brake. Naturally the toolholding fixture also can be arranged at any suitable position ofreduction gear 10 or actuating unit 8.

Although the embodiment of a brake caliper according to the presentinvention shown in the illustrations has both a hydraulic actuatingdevice 7 and an electromechanical actuating unit 8, this is notabsolutely necessary. If the actuating unit 8 and reduction gear 10 aredimensioned sufficiently, i.e. when sufficiently high clamping forcescan be generated, the additional hydraulic actuating device 7 will notbe needed. Due to the engageable freewheel 44, both the driving andparking brake functions can be realized solely by means of theelectromechanical actuating unit.

What is claimed is:
 1. An electromechanically actuated partially lineddisk brake assembly, comprising: a brake caliper, an electromechanicalactuating unit, at least two brake linings that are displaceablyarranged in the brake caliper and act on a friction surface of a brakedisk a multi-step reduction gear that is arranged between the actuatingunit and an actuating element, wherein said actuating unit, multi-stepreduction gear, and actuating element are located in a recess of thebrake caliper that is configured as a housing, wherein the multi-stepreduction gear which is configured as a non-self-locking device, andincludes an engageable freewheel and a rolling-element ramp gear, andwherein the rolling-element ramp gear exhibits a plurality of rampconfigurations, one residing inside another.
 2. A partially lined diskbrake according to claim 1, wherein the rolling-element ramp gearexhibits two ramp halves that can be twisted relative to one another,wherein a first ramp half of said two ramp halves is connected to theelectromechanical actuating unit at the output end and a second ramphalf being operatively connected to the actuating element.
 3. Apartially lined disk brake according to claim 2, wherein the second ramphalf is arranged in a twist-proof manner in the brake caliper.
 4. Apartially lined disk brake according to claim 1, wherein the engageablefreewheel is designed as a return stop effective in the directionopposite to the direction of rotation of clamping.
 5. A partially lineddisk brake according to claim 1, wherein the reduction gear includes aplanetary car connected to the electromechanical actuating unit at thedriving end.
 6. A partially lined disk brake according to claim 5,wherein the reduction gear includes a spur gear connected to theplanetary gear at the driving end and to the rolling-element ramp-typegear at the output end.
 7. A partially lined disk brake according toclaim 1, wherein the actuating element includes a brake piston arrangeddisplaceably in the brake caliper and connected operatively to at leastone brake lining, wherein said brake piston is connected to therolling-element ramp gear at the output end.
 8. A partially lined diskbrake according to claim 1, wherein the actuating element exhibits anadjusting device extendable in the clamping direction of the partiallylined disk brake, which is arranged displaceably in the brake caliper,with said adjusting device being operatively connected to at least onebrake lining on the one hand and connected to the rolling-element rampgear at the output end on the other hand.
 9. A partially lined diskbrake according to claim 8, wherein the adjusting device includes anut-and-spindle configuration that can be twisted relative to oneanother and acts on the brake piston on one side.
 10. A partially lineddisk brake according to claim 9, wherein the nut-and-spindleconfiguration is connected to the second ramp half in a twist-proofmanner.
 11. A partially lined disk brake according to claim 7, whereinthe partially lined disk brake further includes a hydraulic actuatingdevice that is independent of the electromechanical actuating unit. 12.A partially lined disk brake according to claim 1, wherein theelectromechanical actuating unit includes a DC electric motor.
 13. Apartially lined disk brake according to claim 12, wherein the electricmotor includes an angular position sensor.
 14. A partially lined diskbrake according to claim 13, wherein the angular position sensor isdesigned as a Hall sensor.
 15. A partially lined disk brake according toclaim 1, wherein the multi-slip reduction gear includes a tool holdingfixture for an emergency actuating element.
 16. A partially lined diskbrake according to claim 1, wherein the electromechanical actuating unitand the reduction gear are sealed off against their surroundings bymeans of a housing cover attached to the brake caliper.
 17. A partiallylined disk brake according to claim 6, wherein the electromechanicalactuating unit, planetary gear form a first independent subassembly thatis located in a first recess of the brake caliper that is configured asa housing.
 18. A partially lined disk brake according to claim 17,wherein the rolling-element ramp device, and the engageable freewheelform a second independent subassembly that is located in a first recessof the brake caliper that is configured as a housing.